The Dark Forest by Liu Cixin

Book 2 of the sci-fi trilogy “Remembrance of Earth’s Past,” The Dark Forest tells the story of how Earth prepares for invasion by an alien force due in about four centuries. Because of their advanced technology which includes sophons (miniature computers) the Trisolarans know all there is to know about human defense plans. The only hope lies in the fact they can’t tell what people are thinking.

Four Wallfacers are given unlimited power and resources for their duties of developing plans to to defend Earth. But the Trisolarians also have individuals called Wallbreakers whose job it is to find these plans out and inactivate them. Three fail. Luo Ji is the last remaining Wallfacer to try what he can. He had no intention of becoming this but it’s not something one can refuse.
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